Trust, but verify. A Russian phrase made popular by president Reagan fits perfectly when we are talking about testing or QA. Everyone trusts themselves, every programmer or a developer has trust in code. And why shouldn’t they?

But, we know how it goes. In the programming world, even a miniscule mistake could cost a lot. And that is why we have testing.

The front-end ecosystem is advancing and is not getting any simpler. Companies today compete fiercely to hire front-end developers well-versed in their field. With each passing year the intricacies tend to double.

Let’s look at some of the tools to you help in your React.js project

The baseline is choosing the JavaScript test runner. Test runners are an integral part of the testing stack. As a part of our journey being a ReactJs development company, we have seen developers using Karma which helps them suite of tests in one or more browsers at once. They help analyze if the code is safe from browser implementation quirks, providing a level of confidence that is usually unmatched by other solutions. It can also be configured to use remote services like Sauce Labs and BrowserStack.

Another choice for simplicity and ease of use is Mocha CLI. Which is fairly agreeable because Mocha CLI easily runs your Mocha tests in a Node.js environment. Unfortunately, a mechanism to run tests in the browser using the Mocha CLI does not exist.

If you want to perform cross-browser testing or you want to test significant DOM manipulations, go for Karma. Or else, you can use a combination of the default CLI and additional libraries like Enzyme and JSDOM.

JavaScript Frameworks

Make sure your test framework supports testing both asynchronous and synchronous code and make it quite easy to disable the test. Jasmine, Mocha, and Jest meet these requirements.

Jasmine is a behavior-driven development framework for testing your JavaScript code; it doesn't depending on any other JavaScript frameworks, nor does it require a DOM. And it has a clean, obvious syntax so that you can easily write tests.

Here is some sample code from Jasmine.

Jasmine contains assertion abilities, called matchers, baked in. These assertions eliminate the need to include external assertion libraries such as Chai and Should.js. It also allows you to mock functions to cut a few dependency trees out of the scope.

Facebook’s test framework, Jest, was specifically designed for React. Jest responds to basic testing needs pretty well, but the highlight of the day is snapshot testing. It lets you serialize and save the output of components while easily detecting when that output changes. Snapshots are text files saved into source control and checked against future test runs.

Coming back to Mocha, it focuses on being a solid test framework. When you look at it, there aren’t any assertion libraries or fancy types of testing it can do. However, what it does, it does well.

If you choose Mocha, it means you also have to exclusively choose assertion libraries and mocking libraries. You can probably just use Chai and Sinon.js in this case. If you want to look for more options, there is a wiki page for Mocha that outlines the common ones.

In this case, if you do not have special preferences, Jest or Jasmine should be your go-to option. Even though Jest is a general JavaScript testing framework, the snapshot testing feature is exclusive to React components.

Testing Add-Ons

If you want to perform shallow rendering and assertions on the component, there are two options:

React-test renderer for shallow rendering.

React-test-utils for assertions.

There is another option, the Airbnb library called Enzyme. It is a testing utility for React that makes it easier to assert, manipulate, and traverse your React components' output.

Another option is using Sinon.js, a powerful mocking library with detailed assertions. It also provides a great mock implementation of the clock and easy mocking for AJAX requests.